Manufacture and production of artificial threads, filaments, and the like

ABSTRACT

521,148. Artificial silk &amp;c. COURTAULDS, Ltd., and WORMELL, R. L. Oct. 13, 1938, No. 29703. [Class 2 (ii)] Threads which have been formed by extrusion of a solution of casein or like protein substance, e.g. soya bean protein, into a coagulant and have been thereafter treated with a hardening agent are further treated with a salt solution adjusted if necessary as regards its acidity, which brings the pH of the threads to a value at or about the isoelectric point of the protein. The excess moisture is removed from the threads and the latter are then heated in the presence of moisture. The salts used have a buffering action in solution over a pH range in the region of the isoelectric point of the protein, e.g. in the casein about pH 4.6. Sodium phosphate, phthalate, lactate, borate, or acetate, or aluminium acetate or substances forming it, e.g. aluminium sulphate and sodium or calcium acetate maybe used. If acetic acid is liberated in the formation of the solution it may be neutralized with sodium carbonate. The hardening solution may be aluminium sulphate solution or formaldehyde solution. After the hardening treatment the threads may be subjected to the treatment with salt solution with or without intermediate drying. Heating in presence of moisture may be effected in a closed container at a temperature of at least 50‹C. In an example a solution of casein in caustic soda solution is extruded into a salt and acid bath and the fibres are hardened with a solution containing aluminium sulphate, sodium carbonate and acetate, and formaldehyde. The fibres are washed and dried and then immersed in a solution of aluminium acetate made by mixing aluminium sulphate solution with lime and acetic acid, filtering off the calcium sulphate, and adding soda ash to neutralize excess acetic acid. The fibres are removed, whizzed free from excess liquor and heated in a closed vessel. In another example, casein fibres are hardened with aluminium sulphate, stapled, and then treated with a solution of sodium acetate, formaldehyde, and acetic acid. In another example, casein fibres on a conveyer are hardened with a solution of aluminium and sodium sulphates and formaldehyde. The fibres are then stretched in a solution of sodium acetate and acetic acid, wound up on a reel in a bath containing sodium acetate, acetic acid, and formaldehyde. The wound fibres are left in a closed vessel for several hours and then heated. They are then placed in cold water.

Patented Dec. 16, 1941 2,266,672 MANUFACTURE AND PRODUCTION OF ARTI- FICIAL THREADS, FILAMENTS, AND THE LIKE Robert Louis Wormell, Coventry, England, assignor to Courtaulds, Limited, London, England, a British company No Drawing. Application October 27, 1939, Serial No. 301,672. In Great Britain October 13,

This invention relates to the manufacture and production of filaments, threads and the like hereinafter referred to as threads, from casein or the like protein substance. It is known that such threads may be produced by the extrusion of a solution of, for example, casein through a jet provided with a number of holes into a coagulating bath and that after washing the resulting threads it is desirable to harden them by treatment in a bath containing one or more hardening agents such, for example, as an aluminium salt, formaldehyde or natural or synthetic tanning agents in order to render them more insoluble in Water.

The object of the present invention is to treat threads obtained from casein and the like protein substances in such known manner in order to improve their properties particularly their resistance to the action of water or dilute acid at a high temperature.

According to the present invention the process for the treatment of threads which have been formed by the extrusion of a solution of casein or the like protein substance into a coagulant and have been thereafter treated with a hardening agent comprises treating the said threads with a solution of a salt, to which acid has been added which brings the pH of the threads to a Value at or about the iso-electric point of the said protein then removing excess solution from the threads and heating them in the presence of moisture.

Salts which are suitable for use according to the present invention are those which have a bufiering action in solution over a pH range in the region of the iso-electric point of the protein, that is in the case of casein about pH 4.6. Examples of such solutions are those containing sodium phosphate, sodium phthalate, sodium lactate, sodium borate, sodium acetate, aluminium acetate or substances forming aluminium acetate, for example aluminium sulphate and sodium or calcium acetate. If acetic acid is liberated in such solutions it can be neutralised by the addition of sodium carbonate. If an aluminium sulphate solution has already been used in the previous hardening treatment sufficient aluminium salt will have been absorbed by the threads to ensure that on the addition of sodium acetate solution the desired action will take place.

The treating solution may contain formaldehyde or its polymers such as paraformaldehyde. The threads, after treatment in the previous hardening bath, may be deprived of excess liquid in and immediately treated according to the present invention, or they may be washed free from salts and then treated with or without an intermediate drying operation.

After treatment the excess liquid may be re- 6 Claims. (01. 1s--54 carrying out the present invention although the invention is not restricted to these examples.

Example 1 A solution of casein in dilute caustic soda is extruded into a solution containing salt and'acid and the fibres hardened at room temperature in the following bath for 10 hours:

Aluminium sulphate (AI2(SO4)3.18H2O) 50 per cent solution kilogrammes Water litres 14 Soda ash (NazCOs) kilogrammes 3.6 Sodium acetate do 4.4 40 per cent formaldehyde solution do 21 The fibres are then washed in water, dried and immersed in an aluminium acetate solutionmade up as follows:

38 kilogrammes of A12(SO4)3.18H20 solution of per cent strength are added to 2 kilogrammes of lime (Ca(0H)2) and 3 kilogrammes of acetic acid in 12 litres of water. The white precipitate of calcium sulphate is filtered off leaving the aluminium acetate solution. 40 grammes per litre of soda ash are then added to neutralise excess acetic acid formed in the reaction, due to the free sulphuric acid liberated by hydrolysis of the aluminium acetate solution. After immersion for 2 hours in the aluminium acetate solution prepared as above, the fibres are whizzed free from excess liquor and heated in a closed vesselfor 5 hours at 70 centigrade. They are then cooled, Washed with water and dried. On being boiled in water for 30 minutes they are much less damaged and swollen than the unheated material.

Example 2 A solution of casein in dilute caustic soda is extruded into acid and salt, and then taken under tension for about a minute over a series of godets rotating in a bath of aluminium sulphate solution at centigrade. The tow is then cut into staple lengths and placed in a bath of sodium acetate of 30 per cent strength, previously brought to a pH of 5.5 by means of acetic acid. This bath also contains 50 grammes per litre of formaldehyde. The mass of fibres are left in the bath for four hours, whizzed free of liquor and again placed in a bath of the same composition. After four hours the procedure is repeated,

and after a further four hours the fibres are finally whizzed, and heated in a churn for four hours at 90 centigrade. The fibres are then cooled, washed in water and dried. The material so treated has acquired a good resistance to boiling water and boiling dilute solutions of mineral acid.

Example 3 The tow after being cut into staple lengths is treated exactly as in Example 2, but instead of being heated in a churn it is placed in a closed stoppered bottle in an autoclave and heated for 2 hours at 124 centigrade under steam pressure. The resulting product has a good resistance to boiling dilute acid. If there is any slight discolouration of the material after heating in the autoclave this can be substantially removed by bleaching with sodium hydrosulphite.

Example 4 The tow is treated in the bath of sodium acetate and formaldehyde described in Example 2, but instead of changing the bath a number of times, the whole is allowed to stand for 24 hours at room temperature. The mass is then washed free from salt and formaldehyde by means of water. It is then whizzed, and again placed in a bath of 30 per cent sodium acetate of pH 5. After leaving to stand for 24 hours, the fibres are again whizzed, placed in a churn and heated for 4 hours at 90 centigrade. The product has acquired a good resistance to boiling water.

Example 5 A solution of casein in dilute caustic soda is extruded into acid and salt solution. The tow is then dropped continuously onto a conveyor system whereon it is hardened for 45 minutes in a bath containing aluminum and sodium sulphates and formaldehyde. The thread is then taken off the belt and continuously stretched about 200 per cent in an aqueous solution containing 30 per cent of sodium acetate and 2 per cent of aectic acid at 60 centigrade. The tow is then kept under tension for about a minute on rollers rotating in the aforementioned stretching bath and wound up on an aluminium reel rotating in an enclosed bath of 3 parts of sodium acetate 30 per cent solution to which acetic acid has been added to give an acidity of pH 5 and 1 part of 40 per cent formaldehyde solution. The pH of this solution should be about 5. The reel of tow after winding up continuously for an hour is placed in an earthenware pot, with several other reels if desired, and the pot is carefully closed with a tight fitting lid. The whole is then left at room temperature for 24 hours to ensure completion of the hardening process. The pot is then heated to 80 centigrade and left at that temperature for four hours. The reel and threads are then placed in cold water for a short time in order to soften the filaments and remove as much salt and formaldehyde as possible. Finally the tow is either unwound continuously into a large skein and further washed and dried, or cut off the reel and processed in staple form. The final product has not only lost its tendency to shrink thereby increasing in denier and losing strength, but has also acquired a good resistance to boiling water.

What I claim is:

1. A process for the treatment of threads which have been formed by the extrusion of a solution of casein into a coagulant and have been thereafter treated with a hardening agent which comprises treating the said threads with an aqueous solution of a salt, to which solution acid has been added which brings the pH of the threads to a value at about the iso-electric point of, the casein, then removing excess solution from the threads and heating them in the moist condition without allowing the moisture to evaporate and thereafter drying them.

2. A process for the treatment of threads which have been formed by the extrusion of a solution of casein into a coagulant and thereafter treated with a hardening agent which comprises treating the said threads with an aqueous solution of sodium acetate to which solution acid has been added which brings the pH of the threads to a value at about the iso-electric point of the casein, then removing excess solution from the threads and heating them in the moist condition without allowing the moisture to evaporate and thereafter drying them.

3. A process for the treatment of threads which have been formed by the extrusion of a solution of casein into a coagulant and thereafter treated with a hardening agent, which comprises treating the said threads with an aqueous solution of aluminum acetate to which solution acid has been added which brings the pH of the threads to a value at about the iso-electric point of the casein, then removing excess solution from the threads and heating them in the moist condition without allowing the moisture to evaporate and thereafter drying them.

4:. A process for the treatment of threads which have been formed by the extrusion of a solution of casein into a coagulant and thereafter treated with a hardening agent which comprises treating the said threads with a concentrated aqueous solution of a salt of acetic acid to which solution acid has been added which brings the pH of the threads to a value at about the iso-electric point of the casein, then removing the excess solution from the threads and heating them in a closed chamber in the presence of moisture and thereafter drying them.

5. A process for the treatment of threads which have been formed by theextrusion of a solution of casein into a coagulant and thereafter treated with a hardening agent which comprises treating the said threads with an aqueous solution of sodium acetate and formaldehyde to which solution acid has been added which brings the pH of the threads to a value at about the isoelectric point of the casein, then removing the excess solution from the threads and heating them in the moist condition without allowing the moisture to evaporate and thereafter drying them.

6. Process for the manufacture and production of filaments, threads and the like, which comprises extruding a solution of casein through a jet into a coagulating bath, washing the so formed threads, hardening the washed threads by treatment in a bath containing a hardening agent to render them more insoluble in water, cutting the threads into staple lengths, and thereafter treating the staple fibres with an aqueous solution of sodium acetate to which solution acid has been added which brings the pH of the staple fibres to a value at about the isoelectric point of the casein, whizzing the staple fibres free of excess solution, and then heating them for more than an hour in the moist condition without allowing the moisture to evaporate and thereafter drying them.

ROBERT LOUIS WORMELL. 

